Abstract:
Power management is an important concern in sensor networks, because a tethered energy infrastructure is not
available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor
networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy
from the environment. Certain considerations in using an energy harvesting source are fundamentally different
from that in using a battery because, rather than a limit on the maximum energy, it has a limit on the maximum
rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic
manner. While a deterministic metric such as residual battery suffices to characterize the energy
availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source.
Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes
may have different harvesting opportunity. In a distributed application, the same end-user performance may be
achieved using different workload allocations, and resultant energy consumptions, at multiple nodes. In this
case it is important to align the workload allocation with the energy availability at the harvesting nodes. We
consider the above issues in power management for energy harvesting sensor networks. We develop abstractions
to characterize the complex time varying nature of such sources with analytically tractable models and use them
to address key design issues. We also develop distributed methods to efficiently use harvested energy and test
these both in simulation and experimentally on an energy harvesting sensor network, prototyped for this work.